全文获取类型
收费全文 | 373篇 |
免费 | 7篇 |
专业分类
化学 | 228篇 |
晶体学 | 15篇 |
力学 | 19篇 |
数学 | 35篇 |
物理学 | 83篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 20篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 22篇 |
2012年 | 25篇 |
2011年 | 26篇 |
2010年 | 12篇 |
2009年 | 9篇 |
2008年 | 25篇 |
2007年 | 20篇 |
2006年 | 15篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 11篇 |
2002年 | 11篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1963年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有380条查询结果,搜索用时 15 毫秒
1.
Aditya M. Vora 《Journal of Non》2008,354(45-46):5022-5032
A well recognized model potential is used to study the superconducting state parameters (SSP) viz. electron–phonon coupling strength λ, Coulomb pseudopotential μ1, transition temperature TC, isotope effect exponent α and effective interaction strength N0V of some binary metallic glasses of simple, non-simple and transition metals. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru–Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. Instead of using Vegard’s law, pseudo-alloy-atom model (PAA) in the present investigation is proposed and found successful. The present results of the SSP are found in qualitative agreement with other such earlier reported data wherever exist, which confirms the superconducting phase in the metallic glasses. 相似文献
2.
Sukumar Aditya Syamal Bandopadhyay Rebati C. Das Bata K. Nanda 《Thermochimica Acta》1981,46(3):337-340
From rehydration experiments the hydrates Ba(OH)2 · 8 H2O, Ba(OH)2 · 3 H2O β-Ba(OH)2, · 1 H2O, and γ-Ba(OH)2 · 1 H2O have been found in the system Ba(OH)2-H2O. Thermoanalytical measurements (DTA, TG, DTG, high temperature X-ray diffraction, high temperature Raman scattering) on these hydrates are reported. Thermal decomposition of Ba(OH)2 · 8 H2O and Ba(OH)2 · 3 H2O always results in the formation of β-Ba(OH)2 · 1 H2O, the stable form of the monohydrates at ambient temperature. Dehydration of β- and γ-Ba(OH)2 · 1 H2O, both of which form anhydrous β-Ba(OH)2 as the first product of decomposition, starts at 105 and 115°C, respectively. Single crystals of Ba(OH)2 · 3 H2O and γ-Ba(OH)2 · 1 H2O were prepared from Ba(OH)2 · 8 H2O meltings and from ethanolic solutions of Ba(OH)2 , respectively. The crystal data are: Ba(OH)2 · 3 H2O (orthorhombic, Pnma): a = 764.0(2), b = 1140,3(5), c = 596.5(1) pm, Z = 4; γ-Ba(OH)2 · 1 H2O (monoclinic, P21/m or P21): a = 704.9(2), b = 418.4(1), c = 633.3(1) pm, β = 111.45(2)°, Z = 2. 相似文献
3.
The enthalpies of formation of the 2,2′-dipyridinium ion and the 2,2′-dipyridyl-iron(II) complex in methanol—water media at 25°C have been determined by caloriumetry. The entropy-changes have been calculated combining the enthalpy values with the corresponding free-energy changes previously reported. The role of solvents on the thermodynamic parameters has been discussed. 相似文献
4.
Wei ZL Sakamuri S Petukhov PA George C Lewin NE Blumberg PM Kozikowski AP 《Organic letters》2002,4(13):2169-2172
[structures: see text] Both (2S,5R,6R)- and (2S,5R,6S)-6-hydroxy-8-(1-decynyl)benzolactam-V8 were designed and synthesized as PKC modulators. Biological assays reveal the (6R)-ligand to be 20-fold more potent than its (6S)-counterpart in binding to PKC alpha. 相似文献
5.
Enthalpies of formation of 1,10-phenanthrolinium ion and ferrous-1,10-phenanthroline (tris) complex in dioxane—water and ethanol—water media at 25°C have been determined by calorimetry. Results are discussed in the light of ion—solvent and solvent—solvent interactions. 相似文献
6.
The transferability of atomic and functional group properties is an implicit concept in chemistry. The work presented here describes the use of Transferable Atom Equivalents (TAE) to represent molecular electrostatic potential fields through the use of integrated atomic multipole moments that are associated with each TAE atom type used in the reconstruction. TAE molecular surface distributions of electrostatic potentials are compared with analytical ab initio and empirical (Gasteiger) partial charge reference models for several conformations of test peptides. Surface electrostatic potential distributions computed using TAE multipole representations were found to converge at the octopole level, with incremental improvement observed when hexadecapoles were included. Molecular electrostatic potential fields that were produced using the TAE method were observed to be responsive to conformational changes and to compare well with ab initio reference distributions. Generation of TAE atom types and their associated multipoles does not involve fitting to sample electrostatic potential fields, but rather utilizes integrated AIM atomic electron density distributions within representative chemical environments. The RECON program was used for TAE reconstruction. RECON is capable of processing 5,000 drug-sized molecules or 25 proteins per minute per 1.7 GHz P4 Linux processor. 相似文献
7.
Adam D. Martin Jonathan P. Wojciechowski Eric Y. Du Aditya Rawal Holly Stefen Carol G. Au Liming Hou Charles G. Cranfield Thomas Fath Lars M. Ittner Pall Thordarson 《Chemical science》2020,11(5):1375
Peptide-based nanofibres are a versatile class of tunable materials with applications in optoelectronics, sensing and tissue engineering. However, the understanding of the nanofibre surface at the molecular level is limited. Here, a series of homologous dilysine–diphenylalnine tetrapeptides were synthesised and shown to self-assemble into water-soluble nanofibres. Despite the peptide nanofibres displaying similar morphologies, as evaluated through atomic force microscopy and neutron scattering, significant differences were observed in their ability to support sensitive primary neurons. Contact angle and labelling experiments revealed that differential presentation of lysine moieties at the fibre surface did not affect neuronal viability; however the mobility of phenylalanine residues at the nanofibre surface, elucidated through solid- and gel-state NMR studies and confirmed through tethered bilayer lipid membrane experiments, was found to be the determining factor in governing the suitability of a given peptide as a scaffold for primary neurons. This work offers new insights into characterising and controlling the nanofibre surface at the molecular level.The mobility of hydrophobic moieties at a peptide nanofibre surface determines its suitability as a scaffold for sensitive primary cells. 相似文献
8.
Norman G. Gaylord Achyut B. Deshpande Sunit S. Dixit Sukumar Maiti Birendra K. Patnaik 《Journal of polymer science. Part A, Polymer chemistry》1975,13(2):467-482
α-Methylstyrene (MS) and isobutyl vinyl ether (VE) readily polymerize, styrene (S) polymerizes to a small extent, and isobutylene (IB), butadiene (BD), and isoprene (IP) fail to polymerize in the presence of catalytic amounts of AlCl3 when propionitrile, ethyl propionate, and methyl isobutyrate are used as reaction media. MS polymerizes readily and S polymerizes with difficulty in the presence of AlCl3 to yield homopolymers when acrylonitrile (AN) is present and copolymers with ethyl acrylate (EA) and methyl methacrylate (MMA). VE readily homopolymerizes, while IB, BD, and IP fail to polymerize in the presence of AlCl3 and the acrylic monomers. VE readily homopolymerizes, S and MS polymerize to a very small extent, and IB, BD, and IP do not polymerize in the presence of ethylaluminum sesquichloride (EASC) in polar solvents. VE readily homopolymerizes in the presence of EASC and the acrylic monomers. MS polymerizes to a small extent in the presence of EASC and the acrylic monomers to yield equimolar copolymers with EA and MMA and a mixture of cationic homopolymer and equimolar copolymer with AN. S yields equimolar copolymers in low yield in the presence of EASC and the acrylic monomers. IB, BD, and IP in the presence of EASC do not polymerize to any significant extent when EA is present, form AN-rich copolymers and yield poly(methyl methacrylate) in the presence of MMA. A revised mechanism is presented for the formation of cationic, radical, random, and alternating copolymers as well as alternating copolymer graft copolymers in the copolymerization of donor and acceptor monomers. 相似文献
9.
Partha Sarathi Das Basudam Adhikari Sukumar Maiti 《Journal of polymer science. Part A, Polymer chemistry》1994,32(1):39-45
Fluorination of low-density polyethylene, polyacetylene, and poly(vinyl alcohol) was carried out using SF6 gas under electric discharge. The polymers were partially fluorinated and the extent of fluorination was more in the case of poly (vinyl alcohol) than the other two polymers. The fluorinated polymers were characterized by elemental analysis (Fluorine), IR, and x-ray diffraction. Optical transparency of the films was also measured. The fluorinated polymers show better solvent resistance and decreased transparency than the virgin polymer. © 1994 John Wiley & Sons, Inc. 相似文献
10.
N. Sukumar 《International journal of quantum chemistry》1995,56(5):423-432
The dynamics of Jahn–Teller systems has recently been discussed in terms of generalized electronic charge and current densities in nuclear-coordinate space. The introduction of the electronic phase as a function of both electronic and nuclear coordinates, in addition to the electronic density, was a crucial component of this formulation. Here, a densitybased treatment of Born couplings is derived from first-principles quantum mechanics beyond the Born–Oppenheimer approximation. Because of the degenerate electronic configuration of a Jahn–Teller molecule, there are an infinite number of ways in which the charge distribution can be oriented for the same energy, leading to a vanishing bond hardness for the molecule in the symmetric nuclear configuration. Further, the moving nuclear framework serves as the perturbation necessary to define the orientation of the charge density, leading to unhindered rotation of the charge cloud. This leads to the dynamical Jahn–Teller problem, namely, the coupling of electronic and nuclear motions through the Born coupling terms. Applications to superconductivity theory are discussed. © 1995 John Wiley & Sons, Inc. 相似文献